Aqueous release coating compositions for pressure sensitive adhesives

Abstract

Release coating compositions for pressure sensitive adhesive articles, characterized by their excellent properties of remaining migration-free, without the use of an organic solvent, and, that of their ability to be readily separated from the adhesive layer without contaminating the same.

We claim: 
     
       1. A release coating composition suitable for use with pressure sensitive adhesives in rolled form comprising: A. a hydrocolloid stabilized aqueous emulsion of a film forming vinyl polymer having a T g  of from 0° to 60°C. and selected from the group consisting of:   i. a crosslinkable copolymer from at least one crosslinkable monomer with at least one member of the group consisting of vinyl acetate; vinyl acetate and at least one member selected from the group consisting of C 2  -C 18  alkyl esters of acrylic and methacrylic acid, C 1  -C 8  dialkyl esters of maleic, fumaric or itaconic acid, ethylene and vinyl chloride; styrene and at least one C 2  -C 18  alkyl ester of acrylic or methacrylic acid; and vinyl chloride and at least one C 2  -C 18  alkyl ester of acrylic or methacrylic acid; and   ii. an emulsion polymer selected from the group consisting of vinyl acetate homopolymers; copolymers of vinyl acetate and at least one member selected from the group consisting of C 2  -C 18  alkyl esters of acrylic and methacrylic acid, C 1  -C 18  dialkyl esters of maleic, fumaric or itaconic acid, ethylene and vinyl chloride; copolymers of styrene and at least one C 2  -C 18  alkyl ester of acrylic and methacrylic acid; and copolymers of vinyl chloride and at least one C 2  -C 18  alkyl ester of acrylic and methacrylic acid; said emulsion polymer containing a thermosetting resin to effect crosslinking; and   B. from about 0.5 to 20 percent by weight of the emulsion polymer solids, of a release promoting compound selected from the group consisting of:   i. polysiloxanes of the general formula: ##EQU7## wherein R is H or an aryl, higher alkyl or alkyl substituted aryl group containing less than 20 carbon atoms, and x, y and z are integers ranging from 1 to 4; and   ii. organofunctional silicones of one of the following general formulas: ##EQU8## wherein R is an organic spacer other than alkyleneoxy or polyalkyleneoxy, R' is an alkyl or alkoxy group, X is a reactive member selected from the group consisting of hydroxy, mercapto, amino, carboxyl, chloroalkyl, and vinyl, and x and y are integers of from 1 to 4.   
     
     
       2. The composition of claim 1 wherein said vinyl polymer contains mers from a crosslinkable comonomer selected from the group consisting of N-methylolacrylamide, acrylamide, hydroxymethylated diacetone acrylamide, hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, glycidyl acrylate and glycidyl methacrylate to effect crosslinking of said polymer. 
     
     
       3. The composition of claim 1 wherein said vinyl polymer contains 2 to 6 percent, by weight of the emulsion polymer solids, of urea-formaldehyde or melamine formaldehyde to effect crosslinking of said polymer. 
     
     
       4. The composition of claim 1 wherein the hydrocolloid stabilizer is selected from the group consisting of polyvinyl alcohol, hydroxyethyl cellulose, polymethyl vinyl ether of maleic anhydride and polyacrylamide. 
     
     
       5. The composition of claim 1 wherein said part B is present in an amount of 0.5 to 10 percent, by weight of the emulsion polymer solids. 
     
     
       6. The composition of claim 1 wherein said Part A is comprised of a polyvinyl alcohol stabilized vinyl acetate-n-methylolacrylamide copolymer, and said Part B is comprised of from 0.5 to 10 percent, by weight of the emulsion polymer solids, of a polysiloxane having a structure defined by formula I of claim 5 or an organofunctional silicone having a structure defined by formula II(a) or II(b) of claim 5.